An individual, advisor, planner or institutional investor often is charged with managing a portfolio of investments. Such investments in the portfolio may include instruments whose value changes with time, such as stocks, bonds, commodities, etc. Typically, an investor seeks to maximize the value of the portfolio, by buying or holding instruments whose value the investor believes will increase, and selling instruments whose value the investor believes will decrease.
Often, an investor's decision to buy, sell, or hold a particular investment instrument is not exclusively based on numerical data. One area of inquiry is known as “Behavioral Finance,” which studies non-numerical (e.g., psychological or sociological) reasons why investors decide to buy, sell, or hold certain instruments. For example, an investor might have been bought an instrument based on a certain thesis and or price target, however they may continue to hold the security even though the original thesis and or price target has changed due to some form of a behavioral bias.